Electromagnetic contactor with pilot light



1964 J. J. GRIBBLE 3,146,325

ELECTROMAGNETIC CONTACTOR WITH PILOT LIGHT Filed April 17, 1962 2Sheets-Sheet 1 INVENTOR.

4 ATTORNEY.

Aug 1964 J. J. GRIBBLE ELECTROMAGNETIC CONTACTOR WITH PILOT LIGHT FiledApril 17, 1962 2 Sheets-Sheet 2 INVENTOR.

2 J4: ATTORNEY.

United States Patent wire This invention relates to electro-magneticallyoperated circuit control mechanisms and pilot devices therefor, andparticularly to means for providing an alternating voltage source forthe pilot devices which means is operative only during the energizationof the electromagnet of the controller.

For the purposes of illustration, the invention is described herein asembodied in an electric contact device or starter for electricalequipment and employing an electric pilot light which, while lighted,indicates that the contactor has closed a circuit to the equipment.

Heretofore, in electro-magnetically operated starters, the normalpractice has been to provide a pilot light for indicating, whilelighted, that contacts of the contactor are closed and the power circuitcontrolled thereby is energized. For this purpose, a pilot light isconnected in parallel with the magnetic motor coil of the starter.However, in such prior structures, even though the magnetic coil fails,the pilot light continues to be energized.

Again, such a magnetically operated contactor sometimes fails tofunction due to sticking of the-armature operated by its magnetic motorcoil, but the pilot light gives no indication of this malfunctioning.

In accordance with the present invention, the pilot light source ofpower is such that, if the magnetic motor coil of the contactor fails,the pilot light is deenergized and extinguished, thus indicating thefailure. mature sticks in open position, the voltage supplied to thepilot light is reduced with resultant dimming of the pilot lightindicating the improper functioning of the armature.

The source of power for the pilot light is provided herein by a secondrywinding or pilot coil arranged in a closed circuit with the pilot lightand in inductive relation to the magnetic motor coil so that an inducedalternating voltage is produced in the circuit to the pilot light solong as the magnetic motor coil is energized by alternating voltage fromits power source.

Generally, the magnet, armature and coils of contactors and equipment ofthis type are designed to produee a preselected flux. The magnet coil ismodified for producing this preselected flux at the voltage at which thecontactor is to operate. Thus the flux density for an entire line ofcontactors is predetermined for all voltage at which they are to beused. Accordingly, a pilot coil or secondary winding designed for agiven flux density, and a pilot device operable by the voltage inducedby that flux density, can be provided as a sub-assembly for installationin any one of the starters of the complete line.

Furthermore, since the pilot coil is energized by the flux produced bythe motor coil, should the motor coil or its source of voltage fail, thepilot light will be extinguished. Should the armature of the contactorstick in an open position, the flux passing through the pilot coil wouldthereby be reduced, with consequent reduction of the induced voltage, sothat the pilot light would receive less voltage and thus burn dimly,indicating that there is an inadequate source or that the electromagnetcontactor itself is malfunctioning.

Since very little wattage is required for such pilot lights, thesecondary winding, or pilot coil, can be made in the shape of arelatively small, thin, and flat wafer, and hence can be arrangedconveniently at one end or If the ar-,

3,145,325 Patented Aug. 25, 1964 the other of the motor coil insurrounding relation to a portion of the central pole passing throughthe motor coil. It can be made substantially coextensive radially withthe end of the motor coil, and thus can be used conveniently instructures such as disclosed in the copending application of Joseph J.Gribble and Kenneth Marien, Serial No. 120,725, filed June 29, 1961. Forexample, the pilot coil can be readily mounted on the pole piece, andheld in place by the lid of the casing or container of theelectromagnetic contactor or starter therein disclosed.

Various objects and advantages of the invention will become apparentfrom the following description wherein reference is made to thedrawings, in which:

FIG. 1 is a front elevation of a multi-contact contactor embodying theprinciples of the present invention;

FIGS. 2 and 3 are vertical sectional views taken on the lines 2-2 and3-3, respectively, in FIG. 1;

FIG. 4 is a perspective view of the electro-m'agnetic structure of thestarter illustrated in FIGS. 1 through 3; and

FIG. 5 is a schematic illustration of the structure of FIG. 4, includinga wiring diagram.

Referring to the drawings, the electromagnetically operated controlmechanism shown for illustration comprises an electromagneticcontactor'including an E-shaped pole piece 1, an electromagnetic windingor motor coil 2, which cooperates with the pole to operate an armature 3when the motor coil 2 is energized. The armature is provided withsuitable arms 4 which extend downwardly through the coil and at theirlower end are connected to a contact carrier 5, which thereby is mademovable with the armature 3. The carrier carries a plurality of bridgingcontacts 6 which cooperate with complementary stationary contacts 7 in awell known manner. The contacts 7 are fixed in position within a casing8, near the bottom thereof. The casing 8 is arranged to receive theparts described, with the pole piece 1 supported on a suitable shoulder9 in the casing. A detachable cover, or lid, 10 detachably secured inplace by suitable bolts is arranged to bear against the upper end of themotor coil 2 and hold the coil 2 firmly against the pole piece 1 andthereby clamp the pole piece 1 and coil 2 securely in place between thecover 10 and the shoulder 9.

The pole piece 1 is preferably E-shaped, having an inner pole 11 andouter poles 12. The coil 2 is arranged in surrounding relation to theinner pole 11. The E- shaped pole piece has a base portion 13 againstwhich the lower end of the coil bears.

The armature 3 is E-shaped, having a central stem 15 and end fingers 16.The central stem 15 is connected to the arms 4 and is arranged to extendinto the motor coil 2 and move endwise therein as the armature moves toopen and closed positions.

Upon energization of the coil 2, the armature 3 is drawn downwardly and,through the medium of the arms 4, moves the contact carrier 5 to contactmaking position. Suitable return springs 17 are provided in the casingand engage the underside of the carrier 5 and urge it yieldably to openposition so that in case of a power failure the contacts 6 areautomatically opened. The structure thus far described is fullydisclosed in the above identified copending application.

In accordance with the present invention, a secondary winding or pilotcoil 20 is provided and is arranged in inductive relation to the motorcoil 2. In the form illustrated, the pilot coil 20 is in the shape of arelatively flat, thin, annular wafer having the requisite number ofturns to provide the voltage necessary for the pilot device at the fluxfor which the contactor is designed. The motor coil 2 is preferably flatat one end; for example, the end to- Ward the armature. The pilot coil20 is preferably flat and co-extensive with that end of the coil 2 andis juxtaposed in face to face relation thereto, so that it can readilybe assembled .and held in place by the cover of the casing, merely byarranging the cover to bear thereagainst instead of against the end ofthe coil 2;

Although the coil may be located at any suitable location along themagnetic circuit defined by the pole piece 1 and the armature 3, thecoil 20 preferably is arranged so that it surrounds the central stem 15of the armature at the upper end of the coil 2, as illustrated, orplaced at the opposite end of the coil 2 in surrounding relation to theinner pole 11 of the pole piece 1.

Referring next to FIG. 4, the coil 2 is provided with suitableterminaltabs which are connected to external conductors 26 and 27, which connectthe coil 2 to an outside source of voltage indicated by lines L1 and L2through a desired type of switch indicated at 28. The source may be thesecondary of a transformer in inductive relation to the power source ofthe equipment to be controlled.

The pilot coil 20 likewise is provided with terminal tabs, such asindicated at 30 and 31, which are connected in a suitable circuit byconductors 32 and 33 to a pilot device which, in the form illustrated,is an incandescent light bulb 34.

If desired, tabs 30 and 31 may be arranged in a casing 8 so they areaccessible through an opening 35 therein, through which the rating ofthe coils is customarilyjread, as disclosed in said application.

Referring to FIG. 5, which shows the electro-magnetic portions of thedevice, the motor coil 2 is energized from the source L1 and L2 byclosing the switch 28. Energization of the coil 2 energizes the polepiece 11 causing the armature 3 to be drawn downwardly to close thecontacts 6 and 7. The alternating flux produced in the pole piece 1 andarmature 3 by the coil 2 induces an alternatingvoltage in the pilot coil20, which energizes the filament of the bulb 34. The bulb remainslighted as long as coil 2 is energized.

Afilament type bulb is preferred to a gas type bulb as a pilot lightbecause its intensity is greater and it will glow dimly at less thannormal voltage. Furthermore, it can be used with green, blue and purplelenses which are not illuminated by ordinary gas-type bulbs.

As mentioned, another advantage is that, if the armature 3 sticks in anopen position the flux through the coil 20 is less than when thearmature is in the closed position. When the armature is in the openposition, the lesser voltage induced in the coil 20 causes the light 34to glow with much less intensity, thus indicating the malfunctioning ofthe mechanism.

Upon the failure of power from the source L1 and L2, the light isextinguished. If the source L1 and L2 is energized inductively from thecircuit to be controlled, then the pilot failure may indicate a failureof the controlled circuit.

Having thus described my invention, I claim:

1. An electromagnetically operated control mechanism comprising anarmature member, an electrical contact means movable thereby, a magneticpole member, a magnetic motor coil having an axial passage therethrough,at least one of the members having a portion extending into the passage,said members being in magnetic attractive relation to each other whenthe motor coil is energized, means for connecting the motor coil to asource of alternating voltage, a magnetic pilot coil in inductiverelation to the flux of the motor coil,.said pilot coil having an axialpassage therethrough, at least one of the members having a portionextending into the pilot coil passage, said motor coil beingrelativelyfiat at one end, said pilot coil being a unitary structure inthe shape of a thin, fiat wafer, said pilot coil being disposed on saidend of the motor coil in coaxial relation therewith, the foregoingmechanism being mounted in a casing having a removable cover and beingdisposed in the casing with said one end of the motor coil facing towardthe cover, constraining means in the casing engaging the motor coil andconstraining it from movement in a direction away from the cover beyonda predetermined position, abutment means on the cover engaging theadjacent end of said pilot coil and pressing it against said one end ofthe motor coil When the cover is secured to the casing with the motorcoil in said position, and means for detachably securing the cover tothe casing. v

2. The structure according to claim 1 wherein the pole member isE-shaped and its central stem extends into the passage of the motorcoil, the other end of the motor coil is adjacent the base of the polemember, and the armature is E-shaped and its central stem extendsthrough the pilot coil passage.

Great Britain Nov. 25, 1953

1. AN ELECTROMAGNETICALLY OPERATED CONTROL MECHANISM COMPRISING ANARMATURE MEMBER, AN ELECTRICAL CONTACT MEANS MOVABLE THEREBY, A MAGNETICPOLE MEMBER, A MAGNETIC MOTOR COIL HAVING AN AXIAL PASSAGE THERETHROUGH,AT LEAST ONE OF THE MEMBERS HAVING A PORTION EXTENDING INTO THE PASSAGE,SAID MEMBERS BEING IN MAGNETIC ATTRACTIVE RELATION TO EACH OTHER WHENTHE MOTOR COIL IS ENERGIZED, MEANS FOR CONNECTING THE MOTOR COIL TO ASOURCE OF ALTERNATING VOLTAGE, A MAGNETIC PILOT COIL IN INDUCTIVERELATION TO THE FLUX OF THE MOTOR COIL, SAID PILOT COIL HAVING AN AXIALPASSAGE THERETHROUGH, AT LEAST ONE OF THE MEMBERS HAVING A PORTIONEXTENDING INTO THE PILOT COIL PASSAGE, SAID MOTOR COIL BEING RELATIVELYFLAT AT ONE END, SAID PILOT COIL BEING A UNITARY STRUCTURE IN THE SHAPEOF A THIN, FLAT WAFER, SAID PILOT COIL BEING DISPOSED ON SAID END OF THEMOTOR COIL IN COAXIAL RELATION THEREWITH, THE FOREGOING MECHANISM BEINGMOUNTED IN A CASING HAVING A REMOVABLE COVER AND BEING DISPOSED IN THECASING WITH SAID ONE END OF THE MOTOR COIL FACING TOWARD THE COVER,CONSTRAINING MEANS IN THE CASING ENGAGING THE MOTOR COIL ANDCONSTRAINING IT FROM MOVEMENT IN A DIRECTION AWAY FROM THE COVER BEYONDA PREDETERMINED POSITION, ABUTMENT MEANS ON THE COVER ENGAGING THEADJACENT END OF SAID PILOT COIL AND PRESSING IT AGAINST SAID ONE END OFTHE MOTOR COIL WHEN THE COVER IS SECURED TO THE CASING WITH THE MOTORCOIL IN SAID POSITION, AND MEANS FOR DETACHABLY SECURING THE COVER TOTHE CASING.